Apparatus for flamer fuel pressure control

ABSTRACT

A flamer may be used to sterilize poultry litter, soil, concrete, etc. The stationary or mobile flamer disclosed comprises a hood to contain the heat, an external frame, and burners. A fuel tank may be carried on the flamer or on a tractor. An additional embodiment provides for mounting the flamer on wheels, permitting the unit to be towed by a truck, four-wheeler, tractor, etc. The burners are adjustable as to angle, and fueling rate. A pressure in the fuel system is controlled by selectively switching between the liquid and vaporous components of the fuel. By limiting how low the pressure may fall, the flow of fuel from the tank to the torches is more consistent.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a continuation-in-part application of U.S. patent applicationSer. No. 10/687,854, filed Oct. 17, 2003, entitled Mobile FlameSterilizer, and is incorporated by reference herein in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

REFERENCE TO MICROFICHE APPENDIX

Not applicable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a flamer. More particularlythe present invention relates to a fuel supply pressure controller for astationary or mobile flamer.

2. Background Art

Poultry litter may be sterilized by chemical means. As usual, the issuebecomes that of chemical retention and the effect of the chemicals onthe environment. Poultry litter may also be sterilized by flame heat, asdisclosed by Mackenzie in U.S. Pat. No. 3,962,044. Because he disclosesstationary equipment for litter sterilization, the method of Mackenzie'044 requires a significant investment in machinery to handle the litterfor sterilization. Space for the machinery and appropriate shelter isalso necessary.

A tractor drawn flamer was disclosed by Pivonka in U.S. Pat. No.6,014,835 for the purpose of flame cultivation. Because of itsopen-flame design, the flamer of Pivonka '835 is not suitable forsterilization purposes. Because the use of the Pivonka '835 flamer forsterilization was not considered, there was no motivation to make theflamer enclosed for sterilization.

Handheld torches and flamers are available, again especially for weedcontrol and ice melting. These flamers are not suitable for the largetask of sterilizing large amounts of poultry litter or soil, etc. due totheir small coverage and the weight that must be supported or drawn bythe user.

Propane, commonly called Liquified Petrolium (LP), is usually the fuelused for flamers such as those used to sterilize poultry litter. Theequilibrium pressure inside a propane tank containing a saturatedmixture of liquid and vaporous propane is strictly a function of thetemperature of these contents. However, during periods of heavy fuelusage, the pressure inside the tank may fluctuate due to finite timesrequired for boiling off of the liquid into vapor and variations intemperature.

The rate flow of the fuel for a flamer is a function of the tankpressure. When the tank pressure varies, the fuel flow rate varies aswell. Flaming, then, regardless of the purpose, may suffer in quality aslong as the tank pressure is permitted to vary.

A tractor drawn flamer was disclosed by Pivonka in U.S. Pat. No.6,014,835, which is hereby incorporated by reference. This tractor drawnflamer is used for flame cultivation.

A tractor drawn or mounted flamer was disclosed by Pivonka in U.S.Patent Application 2005/0084409 (Ser. No. 10/687,854), which is herebyincorporated by reference. This tractor drawn flamer is used for flamesterilization of poultry litter.

Neither of the above mobile flamers make use of a pressure controlsystem.

There is therefore a need for a fuel pressure control system to use inconjunction with stationary and mobile flamers.

BRIEF SUMMARY OF THE INVENTION

An object of the present invention is to provide control of the fuelsupply pressure for a flamer. Such stationary and mobile flamers may beused, for instance, to sterilize materials such as poultry litter, soil,and pavement; or for weed eradication, or softening asphalt. Tractorsare ubiquitous in the agricultural industry. Because of tractors'versatility, implements are often made to mount to a tractor or be drawnbehind a tractor. Heat has long been used for sterilization. So is itpossible to utilize a tractor for transporting a mobile flamer toprovide heat for sterilization. Such a flamer is mounted on thetractor—preferably on a three-point hitch or quick coupler. Anadditional embodiment of the present invention is represented by aflamer on wheels or skids and drawn behind a vehicle as a trailer.

The fuel supply pressure control system of the present inventionprovides a way to keep the fuel tank pressure near a predetermined valueeven during heavy fuel usage. To effect this control, fuel feed isselected from the vaporous and liquid components of the fuel. When vaporis being drawn from the tank, an equal amount of liquid must boil off toreplace the vapor removed, plus a small volume equal to the volume ofliquid converted to vapor. In contrast, when liquid is drawn off thefuel tank, the volume of liquid is much smaller than the volume of thesame mass of liquid, i.e. the volume of the liquid is much smaller thatthe volume of the vapor. So the volume of vapor that must boil off inthe tank to maintain the fuel tank pressure is greatly reduced.

The fuel supply pressure control system of the present inventionpreferably makes use of a pressure switch, set to make or changecontacts at a predetermined pressure.

This is the pressure set point for the fuel supply. As long as thepressure is greater than the pressure set point, the flamer will utilizevaporous fuel. If the fuel supply pressure drops to or below thepressure set point, the contacts in the pressure switch will change,closing a vapor solenoid valve and opening a liquid solenoid valve, andliquid will be utilized by the flamer. The liquid fuel is vaporizedafter leaving the fuel supply tank. As the fuel travels toward theflamer torches, the pressure rises toward ambient. Boiling of the liquidfuel will result when it reaches the vaporizing portion of the torches,as the fuel attempts to reach an equilibrium state. Hence, at thetorches, the fuel burned is vaporous, regardless of which solenoid valveis open at the time.

Other objects, advantages and novel features of the present inventionwill become apparent from the following detailed description of theinvention when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a perspective view of the tractor-mounted flamer with a fueltank mounted thereon;

FIG. 2 is a side elevation view of the tractor-mounted flamer;

FIG. 3 is a side elevation view of the tractor-mounted flamer;

FIG. 4 is a rear elevation view of the tractor-drawn flamer;

FIG. 5 is a perspective view of a wheel mounted flamer with the fueltank mounted thereon;

FIG. 6 is a perspective view of the underside of the tractor-mountedflamer; and

FIG. 7 is a side elevation view of the tractor-mounted flamer being usedto sterilize a surface;

FIG. 8 is a first piping schematic for a flamer fuel supply pressurecontrol system;

FIG. 9 is a second piping schematic for a flamer fuel supply pressurecontrol system;

FIG. 10 is a first wiring detail for the flamer fuel supply pressurecontrol system;

FIG. 11 is a second wiring detail for the flamer fuel supply pressurecontrol system;

FIG. 12 is a flow diagram of the logic for the flamer fuel supplypressure control system; and

FIG. 13 is a third piping schematic for a flamer fuel supply pressurecontrol system; and

FIG. 14 is a detail of a flamer fuel supply pressure controller.

DETAILED DESCRIPTION OF THE INVENTION

A perspective view of one embodiment of the present invention is shownin FIGS. 1 and 2. A side view and a rear view are seen in FIGS. 3 and 4,respectively. A mobile flamer 100 is shown mounted on an implement hitch105 of a tractor 110. Fuel may, optionally, be carried on the flamer ina fuel tank 120. In a second embodiment, the fuel may be separate fromthe flamer 100, for instance, carried on the tractor in atractor-mounted fuel tank 220.

A hood for the flamer 100 comprises an external frame 130 and skin 140.Because the frame is external to the skin 140, the frame is exposed toless radiant heat transfer, reducing the problems such as oxidation andfatigue caused by high temperatures and thermal cycling. In addition,the flamer 100 can be insulated while maintaining a reflective surfaceinside the flamer because frame 130 members are not in the way.

The skin 140 substantially contains the high temperature gases,protecting the surroundings and concentrating the heat to the materialto be sterilized.

Adjustable skids 150 are used to maintain an appropriate height abovethe litter or other material 700 (see FIG. 7) to be sterilized. Theweight of the flamer 100 may be shifted between the tractor hitch 105and the skids 150, as needed. The flamer 100 is picked up with thetractor hitch 105 and carried off the surface for transport, cooling,etc.

An additional embodiment is shown in FIG. 5 wherein the flamer 100 iscarried on wheels 510 and drawn behind the tractor 110 by its tongue520. The wheels may be drawn up, allowing the flamer 100 to rest on itsskids 150 when in use. One advantage to this embodiment is that theflamer 100 may be towed behind any of a multitude of vehicles such as atruck, four-wheeler, or tractor.

The underside of the tractor-mounted flamer 100 is shown in FIG. 6. Aplurality of burners 610 are arrayed across the front of the flamer 100,the angles of which are adjustable, as shown by the dashed lines. Abarrier 620 may optionally be provided to assist in concentrating theheat, containing the gases, and protecting the surroundings. Anadditional option is shown as a set of rake teeth 630 to loosen and stirthe material 700 being sterilized.

The mobile flamer 100 of the present invention is shown in operation inFIG. 7. The surface material 700 being sterilized may be poultry litter,other livestock manure, soil, concrete, etc.

A schematic of the piping and instrumentation of the flamer fuel supplypressure control system is shown in FIG. 8. Propane is stored in thefuel supply tank 120. A vapor fuel line 805 and a liquid fuel line 810are plumbed into the fuel supply tank 120. Note that this schematic isvalid for mobile and stationary flamers.

Various pressure gages 815 are provided to give insight into the currentoperation of the fuel system. The pressure gages 815 may be electronicand the readings displayed at a central location. The pressure gagereadings may also be incorporated into a sophisticated control system.

Pressure relief valves 820 are provided at various locations throughoutthe fuel system. The pressure relief valves 820 shown in FIG. 8 expeloverpressured fuel into the atmosphere. Another configuration would havethe overpressured fuel piped to torches 825.

The fuel supply control system 800 is shown inside the dashed lines inFIG. 8. The fuel supply control system 800 comprises a vapor linesolenoid valve 830 and a liquid line solenoid valve 835. These valvesare controlled by a pressure switch 840.

A second example of a flamer fuel system is shown in FIG. 9. In thisexample, a shutoff valve 910 is used to positively shut the flamer 100down so no fuel flows.

Examples of the electrical relationships between the pressure switch 840and the solenoid valves 830, 835 are illustrated in FIGS. 10 and 11. Inboth these circuits, a battery 1010 is connected to the pressure switch840 via an on/off switch 1020 which provides a shutdown of the flamer100.

The system shown in FIG. 10 is especially suited for the piping shown inFIG. 8. In FIG. 10, the pressure switch 840 comprises a single poledouble throw pressure switch. The solenoid valves 830, 835 are normallyclosed valves, requiring electrical excitation to open. When the fuelsource pressure decreases to the preset pressure set point, the pressureswitch 840 is actuated, thereby changing the pole to which the battery1010 is connected. At high pressures, the vapor solenoid valve 830 isopen while the liquid solenoid valve 835 is closed. When the pressuredrops to the pressure set point and the pressure switch 840 is actuated,the liquid solenoid valve 835 opens and the vapor solenoid valve 830closes.

The circuit shown in FIG. 11 is suited for use with the plumbingillustrated in FIG. 9. In FIG. 11, the pressure switch 840 comprises asingle pole single throw pressure switch. The vapor solenoid valve 830is a normally open valve, while the liquid solenoid valve 835 is anormally closed valve, requiring excitation to close. When the fuelsource pressure decreases to the preset pressure set point, the pressureswitch 840 is actuated, thereby energizing both solenoid valves 830,835. At high pressures, when neither valve is energized, the vaporsolenoid valve 830 is open while the liquid solenoid valve 835 isclosed. When the pressure drops to the pressure set point and thepressure switch 840 is actuated, providing connection to the solenoidvalves 830, 835, the liquid solenoid valve 835 opens and the vaporsolenoid valve 830 closes.

Because the vapor solenoid valve 830 is a normally open valve and thus,fuel may flow at any time, the additional, shutoff solenoid valve 910 isneeded to provide secure shutoff of the fuel. This shutoff solenoidvalve 910 is a normally closed valve, hence is closes when no power isprovided to it. Note that the secure shutoff solenoid valve 910 may beused with the normally closed solenoid valves 830, 835 illustrated inFIGS. 8 and 10 as well, providing redundant shutoff and the associatedsafety.

Other wiring configurations are possible, and the present invention isnot limited to those shown in FIGS. 10 and 11.

Regardless of whether the fuel is from the liquid or vapor fractions ofthe tank 120, the fuel pressure is dropped through a pressure regulator845. A shutoff solenoid valve 850 is used to turn the flamer 100 offexcept for a small flame, the fuel for which is provided through aneedle valve 855, bypassing the shutoff solenoid valve 850. The smallflame permits the torches 825 to be refired at any time.

In FIG. 12, a logic diagram is shown for the flamer fuel supply pressurecontrol system 800. The fuel supply pressure 1210 is compared to apredetermined pressure set point in a comparator block 1220. Thiscomparison is preferably carried out mechanically in the pressure switch840. If the fuel supply pressure 1210 is greater than or equal to thepressure set point, p_(sp), the vapor solenoid valve 830 is open andvaporous fuel is used 1230 by the flamer 100. If the fuel supplypressure 1210 is less than the pressure set point, p_(sp), the liquidsolenoid valve 835 is open and liquid fuel is used 1240 by the flamer100.

Note that appropriate hysteresis is required in the pressure switch 840to avoid rapid switching between liquid and vaporous fuel.

A second embodiment of the present invention includes the flamer fuelpressure control system 1300 depicted in FIGS. 13 and 14. In thisembodiment, an electronic controller 1310, either analog or digital,accepts a flow signal from a flow transmitter 1320 and a pressure signalfrom a pressure transmitter 1340. Measurement and/or calculation ofthese values are well known to those of ordinary skill in the art. Theelectronic controller 1310 uses these signals to calculate an output foreach of two control valves 1330, 1335. The flow of vapor is continuouslycontrolled by the vapor control valve 1330, while the flow of liquid iscontinuously controlled by the liquid control valve 1335.

The electronic controller 1310 is detailed in FIG. 14. The flow andpressure signals, from the associated transmitters 1320, 1340 are showninput into the electronic controller 1310. A flow set point 1410 is alsoavailable to the electronic controller 1310, adjustable by an operator.The pressure set point 1420 may be predetermined by an operator, or itmay be calculated as a function of a tank temperature signal from atemperature sensor 1350, also shown in FIG. 13. In the usual fashion, asunderstood by those of ordinary skill in the art, errors, ε_(f), andε_(p) for each of the controlled variables, f and p, are calculated inthe respective calculation blocks 1430, 1440. These are utilized in acontrol algorithm or algorithms 1450 such as a pair of ProportionalIntegral Differential (PID) loops with decoupling between the loops, ora multivariable algorithm such as a matrix control algorithm. Thesealgorithms, as well as others, are well known in the art. The presentinvention is not limited to a particular automatic control algorithm1450.

Outputs of the control algorithm 1450 include valve position set points1460, 1470 for each of the two control valves 1330, 1335.

The above embodiments are the preferred embodiments, but this inventionis not limited thereto. It is, therefore, apparent that manymodifications and variations of the present invention are possible inlight of the above teachings. It is, therefore, to be understood thatwithin the scope of the appended claims, the invention may be practicedotherwise than as specifically described.

1-10. (canceled)
 11. An apparatus for providing pressure control for aflamer fuel system using a fuel comprising a saturated liquid-vapormixture, the apparatus comprising: (a) a vapor control valve installedin a vapor fuel line through which saturated vapor fuel is extractedfrom the saturated liquid-vapor mixture; (b) a liquid control valveinstalled in a liquid fuel line through which saturated liquid fuel isextracted from the saturated liquid-vapor mixture; and (c) a pressureswitch having a predetermined pressure set point to selectively switchbetween the vapor control valve and the liquid control valve based on aflamer fuel system pressure.
 12. The apparatus of claim 11 wherein thevapor control valve and the liquid control valve comprise solenoidactuated control valves.
 13. The apparatus of claim 11 including wiringwherein the pressure switch is wired to the vapor control valve and theliquid control valve such that the vapor control valve is open and theliquid control valve is closed when the flamer fuel system pressure isgreater than a predetermined pressure set point and the vapor controlvalve is closed and the liquid control valve is open when the flamerfuel system pressure is less than the predetermined pressure set point.14. An apparatus for providing pressure control for a flamer fuel systemusing a fuel comprising a saturated liquid-vapor mixture, the apparatuscomprising: (a) a vapor control valve installed in a vapor fuel linethrough which saturated vapor fuel is extracted from the saturatedliquid-vapor mixture; (b) a liquid control valve installed in a liquidfuel line through which saturated liquid fuel is extracted from thesaturated liquid-vapor mixture; (c) a pressure sensor to sense a flamerfuel system pressure; (d) a controller having the sensed flamer fuelsystem pressure as an input and having as a first output, a vaporcontrol valve position set point and having as a second output, a liquidcontrol valve set point; (e) a control algorithm in the controller tocalculate the first output and the second output as functions of theinput flamer fuel system pressure to maintain the flamer fuel systempressure at a pressure set point value.
 15. The apparatus of claim 14additionally comprising: (a) a flow sensor for sensing a fuel flow ofthe flamer fuel; and (b) a multivariable control algorithm programmed inthe controller having the saturated mixture flamer fuel system pressureand the fuel flow as inputs and the vapor control valve position setpoint and the liquid control valve set point as outputs.
 16. Theapparatus of claim 11 additionally comprising: (a) a fuel tankcontaining the fuel in the saturated liquid-vapor mixture form; (b) atleast one burner at which a flame caused by a combustion of the fuel isheld; and (c) a hitch to which a flamer is operatively attached to atowing vehicle.
 17. The apparatus of claim 14 additionally comprising:(a) a fuel tank containing the fuel in the saturated liquid-vapormixture form; (b) at least one burner at which a flame caused by acombustion of the fuel is held; and (c) a hitch to which a flamer isoperatively attached to a towing vehicle.